1. Field of the Invention
This invention relates to the chlorination of benzoyl chloride, and, more particularly, it is concerned with a novel process for producing 3-chlorobenzoyl chloride in high selectivity in the absence of a solvent.
2. Description of the Prior Art
In U.S. Pat. No. 3,816,526, there is described a process for halogenating benzoyl chloride in the presence of anhydrous ferric chloride and iodine catalyst in carbon tetrachloride solvent to provide 3-chlorobenzoyl chloride. However, in this process, 13% or more of the benzoyl chloride remained unconverted at the conclusion of the process. Furthermore, significant amounts of dichlorobenzoyl chlorides of undefined purity were obtained. In addition, the process is expensive because the solvent must be recovered and recycled, and because the capacity of a given batch is reduced by the amount of solvent used.
In an article in the Journal of the Chemical Society 121, 251 (1922), the catalytic halogenation of benzoyl chloride in the absence of a solvent gave only a 65% yield of 3-chlorobenzoyl chloride, while 13.5% benzoyl chloride remained unconverted, and large amounts of undesirable by-products were formed.
Accordingly, it is an object of the present invention to provide an improved process for selectively chlorinating benzoyl chloride in the absence of a solvent. More particularly, it is the object of this invention to provide a process which accomplishes the following simultaneously.
1. Maximizes the yield of 3-chlorobenzoyl chloride.
2. Maximizes the ratio of 3-chlorobenzoyl chloride to 2,5-dichlorobenzoyl chloride by-product.
3. Minimizes the amount of unconverted benzoyl chloride.
4. Provides the above without the use of a solvent.